As described in Japanese Patent Gazette No. 2575307, a dump truck is typically equipped with a radiator mounted on the front side of the chassis with a radiator guard installed at the front of the radiator so as to protect the radiator. Such a radiator guard is constituted with a single-peace integrated cover. Japanese Laid Open Patent Publication No. 2003-129847 discloses a cover having a radiator fan sound absorbing function, which is achieved by forming the cover as a noise-suppression duct.